Donald Trump announced his campaign for the Republican presidential nomination by saying the United States needed a leader who had written “The Art of the Deal” — but his ghostwriter said he’s uniquely and disastrously unqualified for the job.

Tony Schwartz, who earned a joint byline and half the bestselling 1987 memoir’s advance and royalties, spent 18 months with the real estate developer and future reality TV star, and he got to know Trump better than almost anyone outside his family.

He’s watched in horror over the last year as Trump’s improbable campaign for the GOP nomination has turned inevitable — and he denounced the candidate in the strongest possible terms in a New Yorker interview.

Here are some of the most horrifying claims made about Trump by his former ghostwriter and confidante:

“I genuinely believe that if Trump wins and gets the nuclear codes there is an excellent possibility it will lead to the end of civilization.”

“One of the most deep and basic needs he has is to prove that ‘I’m richer than you.'”

“He’s a living black hole.”

Schwartz said he would rename “The Art of Deal” if he were writing it today, and would instead call it, “The Sociopath.”

“Trump didn’t fit any model of human being I’d ever met. He was obsessed with publicity, and he didn’t care what you wrote.”

Trump has the attention span of a “kindergartner.”

“It’s impossible to keep him focused on any topic, other than his own self-aggrandizement, for more than a few minutes.”

“If he had to be briefed on a crisis in the Situation Room, it’s impossible to imagine him paying attention over a long period of time.”

“Donald pisses ice water. He’d like people when they were helpful, and turn on them when they weren’t. It wasn’t personal. He’s a transactional man—it was all about what you could do for him.”

“The notion that he’s a self-made man is a joke. But I guess they couldn’t call the book ‘The Art of My Father’s Deals.'”

“Lying is second nature to him. More than anyone else I have ever met, Trump has the ability to convince himself that whatever he is saying at any given moment is true, or sort of true, or at least ought to be true.”

Schwartz deeply regrets his role in helping Trump promote himself, and he’s donating all of this year’s royalties from the book to the National Immigration Law Center, Human Rights Watch, the Center for the Victims of Torture, the National Immigration Forum and the Tahirih Justice Center.

“I’ll carry this until the end of my life,” Schwartz said. “There’s no righting it. But I like the idea that, the more copies that ‘The Art of the Deal’ sells, the more money I can donate to the people whose rights Trump seeks to abridge.”

WATCH: "Art of the Deal" co-author says he now regrets writing it and says it's full of falsehoods. https://t.co/4Z8r6i2bzv